Does port size make a difference?

[Brian2435]

So let's just say(this whole situation is hypothetical) you had two enclosures with equal volume. You also had two cylindrical ports. One with a 2 inch diameter and with a length of 8 inches, and one with a five inch diameter and a length of 15 inches. Let's just also say that both ports would have equal tuning when put in the enclosure. Would there be any sound difference in the two different ports, even though they have the same tuning with the enclosure volume?

[Joe X]

All other things being equal the box with the smaller port will experience higher airspeed, if this airspeed becomes too high then an number of effects appear, first lost efficiency and then turbulence which may hurt a bit sound quality and if the airspeed is really high the port will start generating noise. If the port turns or has sharp edges in it the those effects will appear earlier,

Of course if the subwoofer can't move that much air then those effects may not apperar. There are other slighter effects not mentioned.

[OrionStang]

What if the port is too big, Joe X? What effects will you see then?

[98GCLimited]

^ unloading?

[AMI CUSTOMS]

To the OP, considering all things equal but port area, yes it does affect output, as long as port isn't too big you will generally see increase in output and you increase port area.

[Brian2435]

Thanks for the responses. I saw online that per cubic foot of enclosure volume you should have 15 sq inches of port area. Has anyone heard of anything like this?

[Joe X]

Thanks for the responses. I saw online that per cubic foot of enclosure volume you should have 15 sq inches of port area. Has anyone heard of anything like this?

12 to 16 square inches of port area PER cubic feet of net volume for slot ported boxes, High excursion subs are given more port area so lean towards 16 with those.

It's just a rule of thumb that makes it easy to have a viable port without having use math/modelling oriented methods.

Edited June 29, 2012 by Joe X

[Crandis16]

Thanks for the responses. I saw online that per cubic foot of enclosure volume you should have 15 sq inches of port area. Has anyone heard of anything like this?

12 to 16 square inches of port area PER cubic feet of net volume for slot ported boxes, High excursion subs are given more port area so lean towards 16 with those.

It's just a rule of thumb that makes it easy to have a viable port without having use math/modelling oriented methods.

would you consider a DC lvl 4 m2 12" to be a high excursion sub? if so then I need to redesign!

Edit: sub hooked up to an SAZ-1500D v2

Edited June 29, 2012 by Crandis16

[Brian2435]

Thanks for the responses. I saw online that per cubic foot of enclosure volume you should have 15 sq inches of port area. Has anyone heard of anything like this?

12 to 16 square inches of port area PER cubic feet of net volume for slot ported boxes, High excursion subs are given more port area so lean towards 16 with those.

It's just a rule of thumb that makes it easy to have a viable port without having use math/modelling oriented methods.

Sounds good man thanks

[siucsaluki11]

didn't read the thread, just woke up, and the xanax i ate at bedtime has yet to wear off (its prescribed guys) So I'm kin dad groggy...

But yes, port size makes a hug he difference.

In my blazer, i had a tiny port, hit a 135 on the TL. Built a new box, same amp, same internal volume, same tuning, but bigger port, score went up to 138-9. Built a new box, slightly bigger, and a bigger port still, went up to a 141.xx @37 HZ

Port size DOES matter, no matter what your gf may tell you.